Hello DozyWannabe,
Given that in the Hamburg incident one of the wing fences contacted the ground (possibly as a result of summation of dual input) I'd argue that the reduction in roll authority in those circumstances was probably a good idea!
The BFU state that the continued roll to the left, despite the application of full right aileron, was due to the flight control law switching to ground mode whilst the aircraft was still technically airborne.
The crew needed more than half aileron to control the roll - but the computer logic denied it.